A solar panel, as is known in the art, is a device for collecting solar energy and converting solar energy into electrical energy. When the solar panel is shaded by clouds or leaves, a shadow region is formed on a portion of the solar panel. A shaded solar panel produces a hot spot effect in which the solar panel is burned, impairing functionality of the solar panel. Bypass diodes in a photovoltaic junction box mounted on the solar panel prevent the solar panel from being burned by the hot spot effect.
FIGS. 1 and 2 show a photovoltaic junction box known in the prior art. The photovoltaic junction box has a box body 100′ with four terminals 210′, 220′, 230′, 240′ and three diodes 310′, 320′, 330′ arranged in the box body 100′. Each of the three diodes 310′, 320′, 330′ is mounted between adjacent terminals 210′, 220′, 230′, 240′. A conductor core 11′ of a positive wire 10′ introduced into the box body 100′ is directly electrically connected to the terminal 210′, and a conductor core 21′ of a negative wire 20′ introduced into the box body 100′ is directly electrically connected to the terminal 240′.
As shown in FIGS. 1 and 2, each of the three diodes 310′, 320′, 330′ has a positive pin 311′, 321′, 331′ and a negative pin 312′, 322′, 332′ soldered on the adjacent two terminals 210′, 220′, 230′, 240′, respectively. A soldering bottom surface of each negative pin 312′, 322′, 332′ is larger than that of a soldering bottom surface of each positive pin 311′, 321′, 331′. The positive pin 311′ of the diode 310′ is soldered on the terminal 210′. The negative pin 312′ of the diode 310′ is soldered on the terminal 220′. A chip (not shown, which is packaged in a package body) for the diode 310′ is directly soldered on a top surface of the negative pin 312′ of the diode 310′. Since the area of the soldering bottom surface of the negative pin 312′ of the diode 310′ is larger than that of the soldering bottom surface of the positive pin 311′ of the diode 310′, the heat generated by the chip for the diode 310′ in use is mostly transferred to the terminal 220′ via the negative pin 312′.
As shown in FIGS. 1 and 2, the terminal 220′ receiving most of the generated heat is not directly connected to the conductor 11′ of the positive wire 10′, and consequently, the heat transferred to the terminal 220′ cannot be rapidly dissipated to an area external of the box body 100′. It will lead to the diode 310′ being burned due to overheating. Once the diode 310′ is damaged, the diode 310′ cannot play a bypass role, and the solar panel will be burned due to the hot spot effect.